The invention relates to an electron gun assembly having a reinforced heater tab which minimizes cathode-ray tube failure caused by a shorted heater tab.
U.S. Pat. No. 3,555,640 issued to Lundvall on Jan. 19, 1971 discloses a method for mounting a heater within a tubular cathode. A U-shaped tab is welded to the legs of the heater, and a transverse portion of the tab is removed after the heater is positioned within the tubular cathode. The removal of the transition portion electrically isolates the arms of the tab so that the heater can be energized. The tab is shown as substantially flat; however, a step-like offset of the heater tab is shown in U.S. Pat. No. 4,523,124 issued to Blanken et al. on June 11, 1985. The off-set facilitates centering of the heater within the tubular cathode and permits thermal expansion of the tab structure during tube operation but provides little structural strength.
A conventional heater tab 10 hereinafter referred to as a conformal tab is shown in FIG. 1a. The conformal tab 10 comprises a main body portion 12 including a first part 14 and a second part 16 which are temporarily connected, during electron gun construction, by a removal portion 18 located below a score line 19. As shown in FIG. 1b, the conformal tab 10 includes a pair of outwardly directed feet 20 each of which is connected to the parts 14 and 16 of the main body portion 12 by substantially orthogonal legs 22 extending therebetween. A pair of heater legs 24 for a heater 25 are attached, for example by welding, to the parts 14 and 16. A problem with the conformal tab 10 is that sufficient transverse motion of the parts 14 and 16 in the direction A-A, subsequent to the removal of portion 18, can cause the parts 14 and 16 to contact one another and short-out the heater. Thus, there is a need for a reinforced heater tab that is structurally strong yet easily weldable to support components within the electron gun assembly.